1. Field of the Invention
The present invention relates to a floor covering with a strong noise-reducing effect for the interior trim of means of transport.
2. Description of the Related Art
In DE 197 54 107 C1 and the prior art cited therein, which is incorporated herein by reference, the absorption behavior of microperforated building elements is examined. In the specification mentioned, baffle structures composed of layers of microperforated sheets which are pending from a ceiling or a roof as so-called compact absorbers are examined. The microperforated sheets are suitable for very efficiently absorbing from the space sound waves impinging on one or both sides normally, at an angle or in a grazing manner, especially at higher frequencies.
Further, structures are known in which a sound-impermeable surface is provided with perforations to achieve an absorptive effect of the underlying absorber, see, for example, DE 30 18 0172 A, DE 41 23 593 A and WO 92/01587.
DE 295 07 971 U1 relates to a floor damping system for automobiles having a porous carpet floor structure, without stating hole sizes.
DE 299 15 428 U1 relates to a sound screening element for protection from sound propagation from the noise area of, in particular, motor vehicles and other machines and devices using a layer having a multitude of openings, characterized in that the layer is formed as a self-supporting sound-protection molded part and has a hole area ratio (LV) of between 0.001 and 20% at a thickness (d) of the molded part of between 0.02 and 50 mm and an average width (b) or an average diameter (D) through openings of between 0.001 and 2 mm.
DE 92 00 439 U1 relates to a non-crush rigid molded part, especially for the floor area in the passenger compartment of automobiles, which has a substructure layer which is stable under load and made of a rot-resistant first plastic material and a decorative layer provided towards the viewing side over said substructure layer and made of a second plastic material or natural material and optionally one or more sealing layers provided between said substructure layer and decorative layer and/or on the backside of said substructure layer and made of further plastic materials, wherein all the layers are laminated to form a multilayer structure. The molded part is characterized in that said substructure layer has a fibrous component and a thermoplastic binder component distributed therein whose proportion is suitable for producing the required stiffness of the molded part.
DE 39 05 607 A1 describes a layer structure for the preparation of sound insulations and a method for their preparation. For this purpose, the acoustically effective layer consists of a thermodeformable absorbing plastic which can be processed into a foam and/or at least one layer consisting of a non-woven. The layer structure and the sound insulation produced with it can be employed, in particular, for the floor covering of motor vehicles.
The floor coverings employed in the automobile field integrate different functions which must be considered in the preparation: aesthetic demands (surface appearance, pleasant feel), leveling of surface contours of the body, acoustic functions (damping, absorption and insulation), optimum use properties (minimum wear, high crush resistance, good cleanability, high light resistance), foam-integrating of additional structural parts (attachment of floor mats, parts for increasing crush resistance), openings for rear heating and for wire troughs, application by welding of crush protector and foot rest. In these considerations, suitability for process also is to be ensured: extreme deep-drawability without loss of functionality, through-foaming resistance of the material structure, recyclability. In recent times, the emission behavior is hugely gaining importance. Thus, the material structure of a floor covering in the automobile field which is usual today is as follows:
Pile/tufting support/bonding/backing adhesive/heavy sheet/cover fleece/soft foam. In middle class and luxury class vehicles, tufting velours qualities are employed, and in compact class vehicles, flat-needle webs and dilours qualities. Also, flocked, knitted, machine-knitted and woven materials as well as malivlies are found here. As a coating, latex and polyolefins (especially PE) as well as thermoformable non-woven constructions are employed. Instead of a PUR soft foam (with specific gravities of ≧60 kg/m3), loosely compressed textile fibrous non-wovens with thermoset or thermoplastic bonding as well as combinations of foam or non-woven layers having different flow resistances are also employed. The sound absorption property of the floor covering can be increased when a porous layer which is open to air and thus to sound is inserted between the actual top web and the process-caused sealing layer or heavy sheet. As the porous layer which is open to air and thus to sound (absorption layer), polyester and mixed fiber non-wovens are employed here; to prevent the entry of water into the material structure of the floor covering, the latter is furnished with a hydrophobic property. The sealing sheet which is often employed in addition to the heavy sheet is supposed to prevent the breakthrough of foam in foam backing. For saving weight, today, the heavy sheet (the specific gravities are between 0.8 and 10 kg/m2) is also in some cases completely dispensed with, depending on the engine and body designs, in which case only sealing sheets (multilayer sheets with specific gravities of between 0.04 and 0.35 kg/m2) are employed.
It is disadvantageous in all known floor coverings that sound absorption is restricted solely to the surface and a thin sublayer and thus absorption can become effective only conditionally.